Musk jokingly added that they used a 1,000-mile long extension cord, but he is actually referring a system made of extension cords that they have used to charge Tesla Semi prototypes at Tesla’s regular charging stations.

Tesla Semi is supposed to eventually used its own network of ‘Megachargers’, which can enable a higher charge rate than the Superchargers, but those new stations have yet to be deployed.

People who have witnessed Tesla Semi prototypes charging at Supercharger stations have told Electrek that the system made of extension cords plugs into several Supercharger stalls at the same time and into several charge ports on the truck.

They weren’t able to take any picture of the contraption aside from the one we see above.

It sounds like it’s enabling Tesla Semi to travel very long distances – purely on electric propulsion.